Safety control system for oil burners



Jan. 15, 1952- 'J, c, GlBsON 2,582,827

SAFETY CONTROL SYSTEM FOR OIL BURNERS Filed May 2, 1946 6 Sheets-Sheet l INTOR.

1952 J. c. GIBSON 2,582,827

SAFETY CONTROL SYSTEM FOR OIL BURNERS Filed May 2, 1946 s Sheets-Sheet 2 Ill INVENTOR.

Jan. 15, 1952 7' J c, som 2,582,827

7 SAFETY CONTROL SYSTEM FOR OIL BURNERS Filed May 2, 1946 6 Sheets-Sheet 5 IN V EN TOR.

Jan. 15, 1952 Filed May 2, 1946 J. C. GIBSON SAFETY CONTROL SYSTEM FOR OIL BURNERS 6 Sheets-Sheet 4 jive/22 071 Jan. 15, 1952 J. c. GIBSON 2,582,827

- SAFETY CONTROL SYSTEM FOR OIL BURNERS Filed May 2, 1946 6 Sheets-Sheet 5 J IN V E? 0R. e

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Jan. 15, 1952 J, c, GlBSON 2,582,827

SAFETY CONTROL SYSTEM FOR OIL BURNERS Filed May 2, 1946 6 Sheets-Sheet 6 v 5211 22 2 0i; cfefferaozz/ 6. @2590];

Patented Jan. 15, 1952 UNITED STATES PATENT OFFICE SAFETY: QQN'LROL @XSTEM FOR 01L. BURNERS" Jefferson Gibson, hicigfi, Application May, 2 1946, Serial No. 666,693

The present invention relates to improvements in liquid fuel burners, and more particularly to improvements in an automatically operatedfueloil burner adapted to burn low grade, viscous which is relatively inexpensive to manufactureand to operate, yet which efii'cient over a wide range of heating loads.-

, Another object of my invention isto provide inexpensive and efficient means for imposing a program of automatic operation upon the elemerits of a liquid fuel burner.

Still another object of my invention isto provide improved automatic safety controls in a liquid fuel burner.

Yet another object of my invention is to pro-- vide in a liquid fuel burner improvedautomatic means for pre-heatingv the liquid fuel prior to delivery. at a combustion point. I

A further object of my invention is to: provide in a liquid fuel burner a control circuit which produces an automatic cleaning of the combus tion points of excess fuel after each periodv of combustion in order to prevent carbonization and clogging at said points,

The foregoing and such other advantag.es,- objects and capabilities as may appear herein or be pointed out as this description proceeds, or as are inherent in the present invention,, are illustrated in the accompanying drawings. which:

Figure 1 is a schematic representation ofthe' parts in the fuel and air supply systems illus-' trating the flow of fueland of air through my: invention, and the relative position of .thezparts in said systems;

Figure 2 is a right side elevation of the control cabinet with the side panel removed to show thearrangement of parts inside said cabinet;

I Figure 3 is a plan view of the'control cabinet with the top panel removed andv the front panel broken away;

Figure 4 is a view in vertical section through the pre-heating bath showing the oil: and air pumps, the fuel carrying coil, and theelectrical pre-heating unit immersed in said, bath;

Figure 5 is a view in vertical, transverse section Figure 7 is a partial rear elevation of the front panel of the control cabinet illustrating the trio of liquid contact switches which control the auto matic program. and the safety control liquid contacts'witch; n

Figure 8 is a side elevation of the safety control liquid contact switch, the electrically-heated bimetallic element cooperating therewith, and related parts;

Figure 9 is a side elevation of thebimetallic helix assembly which is positioned in the furnace with the combustion nozzle; and

\ Figure- 10 is a front elevation of the bimetallic helix assembly of Figure including the liquid contact switch made and broken by said helix.

Like reference characters are used to designate similar parts in the drawings and in the description of invention which follows.

The path taken by the fuel oil through the burner is bestpresented by the schematic flow diagram of Figure 1. The fuel oil enters the burner from a storage tank (not shown) in the line ;49= through the valve 59. From the valve 50 the fuel oil is drawn in the line 5i through the strainer 52 into the fuel oil pump 53. Onthe, pressure side of the pump 53 the fuel oil is propelled in the line 54 into the fuel oil chamber 55 which fulfills a heat exchange function hereinafter described. The flow of fuel oil divides upon leaving the chamber 55; one branch line 56' leading the fuel oil to the pre-heating coil 51, thence through the fuel supply solenoid valve 58, and preferably through an auxiliary strainer 59, and past afuel meter es into the line 33 to the combustion nozzle 22 where said fuel oil is car of the valve 62- by the handle 42 controls the amount of fuel oil delivered to the combustion point: and regulates the caloric output of the burner. For example, if the: burner is to be used to heata small bungalow, the valve 62 is openedwidely to lower the pressure in the chamber 55. Thus, most of the fuel oil recirculated between the-pump-M and the-chamber 55 and only a small proportion of the fuel oil is propelled into the combustion lines 56 and 33 and burned. If the bffi neri's td-be usedto heat-a'fifty apartment burner. The air is taken into the system through I the air filter 63. From the filter 63 the air is sucked in the line 64 into the air pump 65 and propelled from said pump 65 in the line 66 into the air chamber 61 which damps the pulsations in the air lines produced by said pump. From the chamber 6'! an air line 68 leads to a large accumulator tank 69. The chamber 61 is also tapped by the air line 32 leading to the combustion nozzle 22 where the air is mixed with the fuel oil and the mixture is ignited.

system for preheating both the fuel oil and the primary air prior to combustion. This preheating system is also best illustrated in Figure l. I utilize the heat generated by the oil pump I 53 and the air pump 65 to warm an oil bath I0. This bath I is contained in a tank II and most of the elements of the oil and air supply systems are arranged within said tank ll to be immersed in said bath I0 so that the fuel oil and air en route to the combustion point have ample opportunity to absorb heat from said bath I0. Advantageously, oil may be supplied to the bath I0 from the reservoir I2 of lubricating oil in the air accumulator tank 69. The air pres-' of lubricating oil from' the bath I0 is carried by the primary air fromthe pump 65 into the chamber 61 from which said oil drips back down the line 68 into the reservoir I2.

It is apparent from Figure 1 that the fuel oil is first warmed in the strainer 52 which is immersed in the bath I0. The fuel oil is thus thinned immediately upon entering the burner system thereby settling out sediment, facilitating filtration, and requiring less vacuum from the oil pump 53 to draw said oil through the fuel-lines 49, and 6|. The fuel oil is warmed again in the pump 53, in the heat-exchanging chamber 55, and in the preheating coil 57, all of which elements are immersed in the bath 10. While passing through the pre-heating coil 51, in addition to the heat of the bath I0, the fuel oil also absorbs heat from the electrical pre-heating unit I4 during the phases of the burner cycle wherein the pumps 53 and 65 are not operating and not generating heat. The electrical pre-heating unit "I4 is automatically energized during the aforesaid phases of the burner cycle in a manner presently to be described. The result of the cumulative pre-heating of the fuel oil in my invention is a fuel oil temperature of 160 F. to 180 F. in the nozzle 22 at the start of the combustion period. These temperatures will drop no more than to F. during the combustion period when the electrical pre-heating unit I4 is de-energized and the fuel oil is pre-heated by the lubricating oil bath I0 alone. Since the primary air is also pre-heated in the said pump 65 and the chamber 61, the fuel oil is not cooled in carburation and I attain remarkably complete combustion and fuel economy in my burner.

The relative arrangement of parts within the '4 cabinet 20 is best shown in Figures 2, 3, 4 and 5. Figure 2 illustrates the electric motor I5 which drives the pumps 53 and 65 through the sheaves l6 and I7 and the V-belt I8. The transformer 19 steps-up the voltage of a source of electrical power to bridge a spark gap in the ignition system presently to be described. A fuse block 8 is positioned beside the transformer I9. The air line 8| (also shown in Figure 1) leads from the chamber 61 to the air pressure gauge 4| on the instrument panel 39. The fuel oil line 62 (Figure .1 also) leads from the chamber 55 to the fuel oil pressure gauge 40 on the panel 39. Figures 3, 4 and 5 show the relative positions of parts described above within the lubricating oil bath I0.

The operation of my burner is fully automatic so that it requires no attention other than the closing of the main line switch I03 at the beginning and end of the heating season. The program of automatic and safety control is estab- An important feature of .my invention is the lished in my burner by the combination in the electrical circuit of Figure 6 of the electrical, mechanical and thermal elements illustrated.

The rotation of the main line switch handle rotates the bell crank I01 which in turn flicks the switch button I08 (Figure 7). The switch button I08 makes and breaks the main line switch I09 (Figure 6). If my burner is to be used to heat a building, a house thermostat H0 is inserted in a circuit III between the main line leads H2 and H3. If my burner is to be used in an industrial furnace, an auxiliary switch I I4, is inserted in the circuit III. Both the thermostat H0 and the auxiliary switch H4 are shown in parallel in the circuit III in Figure 6. The circuit l I I also includes an incandescent bulb H5 and a. liquid contact switch exemplified by the mercury-in-glass tiltable switch H6. The incandescent bulb H5 is embraced by a bimetallic helix HI (Figure 7) which expands in response to the heat emitted by said bulb H5 when said bulb is electrically energized.

Still referring to Figure 7, three mercury bulb switches H8, H9 and I20 are mounted in spring clips I2I, I22, and I23. Clips I2I and I23 are welded to clip I22 which in turn is fastened to the helix H1. The switch H8 is mounted to be made when said helix I I! is cool and broken when said helix I I1 is heated. The switches H9 and I20 are mounted upon said helix H1 in opposite phase relationship from switch H8. In other words the switches H9 and I20 are broken when the switch I I8 is made, and vice versa.

The mercury bulb switch H8 is connected in the circuit I24 in series with the electrical preheating element I4 between the main line leads I I 2 and I I3 (Figure 6). The mercury bulb switch I I9 is connected in the circuit I25 in series with the electric motor I5 between the main line leads H2 and H3. The mercury bulb switch I20 is connected in series with the solenoid I26 of the fuel supply valve 54 in a branch circuit I2I leading to the circuit I II and then to the main line lead II 2. The switch I20 is also in series with the primary coil of the step-up transformer I9 in a circuit I28 branching again from the branch circuit I21 to the main line lead H2. The secondary coil of the transformer I9 is connected across the fuel igniting spark gap I03. The circuit I 28 does not include the solenoid I26.

In a circuit I29 between circuits III and I2! and shunted about the solenoid I26 is yet another mercury bulb switch I30 and a bimetallic resistance element I3I which moves in response to heat generated in itself when electrically energized. The switch I30 is mounted upon a second 5. bimetallic helix I32 illustrated in Figures 9 and 10. The bimetallic helix I32 projects into the firebox beside the nozzle 22 and moves in response to changes in the heat within saidfirebox. A shield i33 protects the helix I32 fromdirectcontact with the combustion flame and tends. to absorb the heat of combustion and reflect said heat evenly upon said helix I32. A rod I34 is fastened at one end I35 to thehelix I32 and. ex-

tends longitudinally through said helix. A spring clip I30 projects from a fork I31 journaled upon the other end I38 of the rod I34 and said clip I30 embraces the mercury bulb switch I30. Ex pansion and contraction of the helix I32 rotates the rod I34 in turn making and breaking the switch I30. When the helix I32 is heated, the switch I30 is broken; when said helix I32 is cooled, the switch I30 is made. Rotation of the clip I30 and switch I30 is limited by the stop pin I39 in the embrace of the fork I 31.

Figure 8 discloses the cooperation of parts with the mercury bulb switch H in the circuit III. The switch I I6 is held in a spring clip I40 rotata- 'bly mounted upon a shaft I4I projecting from the rear face of the instrument panel 33. A weight I42 is fastened to the clip I40 remote from the switch H6. The clip I40 is held in a position with the weight I 42 carried high and the switch i It carried low by pointed'pin I43 socketed in said clip at I44. Said pin I43 is fastened to the free end of a flexible arm I45 slidably journaled upon the shaft l4l. The flexible arm I45 is fastened to the bimetallic resistance element I3I by the pin I40. When current is permitted to flow in said element I3I, heat is generated therein and the element expands, flexing the arm I45 away from the clip I40. The pointed pin I43 is pulled from the socket I44 and the weight I42 rotates the clip I40 and breaks the switch IIG for a purpose hereinafter discussed. a

A helical spring I41 on the shaft MI is tensioned between the spring arm I45 and the nut I48. Tension in the helical spring I41may be adjusted by rotation of the nut I40. The adjustment of the tension in said helical spring I41 fixes the period of time required for the bimetallic resistance element I3I to break said switch IIG after said element I3I. is energized. Once broken, the switch Hi can be remade only by upward movement of the reset handle 45.

Said upward movement. of the reset handle 45 I returns the reset handle 45' to its original" position.

Connector block I52 and I53 on the rear face of the panel 39 (Figure 7) furnish convenient means for connecting the above-described elements into the circuits of Figure 6 in which figure the mercury switches are shown in burner running position. When said circuits, are established, the following program of automatic operation and safety control is imp'os'edupon the burner. Assuming the burner is to be used in heating a dwelling place, the main line switch I09 is closed at the beginning of the heating season. A source of electrical power is thus brought across the lead lines H2 and H3 (Figure. 6). The mercury bulb switch *8 is in the made position and current will flow in the cir cult I24 through the electrical pre-heating-ele-- 6 ment14 generating heat to warm the fuel'oll in the fuelpre-heatingcoil 51'. This phase of 0perati'on continues untilthe house thermostat I I0 calls for heat by closing the circuit III, whereupon the incandescent bulb Il5 is energized and begins heating the bimetallic helix II1. Approximately one and one-half minutes later, the bimetallic helix H1 has responded sufficiently to the heat of the bulb II5 to break the mercury bulb switch H8 and to make the mercury bulb switches H9 and I20. This cuts off the current in circuit I24 and ole-energizes the electrical preheating element 14. The making, of switch H9 causes current to flow in circuit I25, thereby causing-the electric motor to drive the pumps 53 and 65. The pumps 53 and t5 generate heat in their operation and this heat is absorbed by the oil bath I0 and is thus utilized to warm the fuel oil supplyelements immersed therein. The making of switch I causes currentto flow in circuit I28, thus energizing the transformer 15 and creating a fuel ignition spark across the gap I03. The making of switch I20 also causes current to fiow in circuit I21 actuating the solenoid I and opening the valve 58, thereby admitting fuel oil to the car-burating chamber 30. In the meantime, the air pump 05 has been building up pressure in the chamber 61 and accumulator tank 53. The pressure in the tank 60 commences the circulation of the lubricating oil. Since it takes a short time to build up pressure in said tank 69, relatively little primary air is initially pumped to the carburating' chamber 00 and the mixture reaching the ignition spark is rich in fuel oil at the start of the combustion period. The mixture is progressively cut by more primary air as air pressure builds'up during the initial phase of the combustion period. Thus, I have established an automatic choke in '1 my burner making for faster ignition by providing a relatively richer fuel mixture at the start of the combustion period.

I have noted previously that when there is no flame in the firebox and the bimetallic helix I32 v is cool, the mercury bulb switch I is in the made position. Thus, when the mercury bulb switch I20 is also made at the start of the cornbustion period, current will flow in the shunt circuit I29 energizing the bimetallic resistance element I3I. Ina short'periodof time, depending upon the adjustment of the helical spring I41 (FigureS), the heating of the bimetallic resistance element I3I will cause the same to move sufficiently to break the mercury bulb switch i It -unless the flame has caught in the firebox and heated the bimetallic helix I32, thereby breaking the switch I30 and de-energizing the bimetallic resistance element I31. The breaking of the switch III; will cut the current in, circuits III and I21, thus turning off the incandescent bulb H5 and actuating the solenoid I20 to close the fuel supply valve 50. Approximately one and one-half minutes later, as the bimetallic helix. 1 cools, the switches H0- and I20 will break, tie-energizing the electric motor 15 and. spark gap I03. Thus, it is apparent that, if for any reason the ignition fails to catch a flame. in the firebox, my burner will automatically turn itself on? after a pre-determined brief period of. time.

The same sequence of operations will turn my burner off automatically if the flame in the firebox fails for any reason during the. combustion period. I prefer to adjustthe helical spring I41 in such tension whereby, the switch I I6 is broken approximately three and one-half minutes after 7 the flame fails in the firebox, but it is understood that this period of time may be varied according to the safety requirements of the installation.

The program of automatic control of my burner includes an operational phase of cleaning the nozzle tip of excess fuel oil after each combustion period. When the house thermostat llil cuts the circuits HI and I21, the solenoid I26 is actuated immediately and the fuel 1 oil supply is cut at the valve 58. However, the electric motor continues to drive the pumps 53 and 65 for approximately one and one-half minutes while the bimetallic helix ll'l cools enough to break the switches I I9 and I20. Thus, for approximately one and one-half minutes immediately after the fuel supply is cut off each time, a blast of air cleans the nozzle tip of excess fuel oil. Carbonization and clogging at the nozzle tip is thus minimized, and the combustion nozzle thus requires practically no manual cleaning.

In the construction and operation of my invention above described, I achieve many objectives highly desirable in liquid fuel burners. It is apparent that my burner is adapted to a Wide range of heating loads, since the regulation of the fuel supply valve 62 serves to deliver small or great quantities of fuel oil to the combustion nozzle or to a bank of such nozzles. of relatively small volumes of primary air under considerable pressure, I attain complete combustion near the monoxide stage. All of the primary air is consumed in the combustion, none remaining to cool the flame or to push the heat through the firebox to be dissipated up the stack. Remarkably low stack temperatures are experienced with the use of my burner. The low velocity of air through the firebox produces a soft, clinging fiame therein that economically distributes the heat evenly throughout the firebox.

The lcw stack temperatures characterizing the use of my burner obviates the concurrent use of a conventional stack switch as a safety control. However, I have found that the insertion of the bimetallic helix I32 directly into the firebox serves a distinct advantage. The high temperature of the firebox burns away carbon deposits tending to form on the helix, thereby eliminating the carbonization disadvantage of a stack switch. Furthermore, the burner is more compact, and the safety controls are easier to reach for inspection and repair in the furnace than an equivalent set of controls in the stack.

The pre-heating' of both fuel oil and air is accomplished economically yet eificiently in my burner by utilizing the heat generated by the pumps 53 and 65. The preheated fuel oil which is not burned is re-circulated through the oil pump 53 and no heat is lost by return of preheated fuel to the storage tank. The high preheating temperature attained in the fuel oil permits the use of cheaper fuel oils of relatively high viscosity. The pre-heating of both fuel oil and air results in more complete combustion. Since the fiame is not cooled by injection of cold primary air, greater economy of heat is attained in the furnace.

The automatic control system of my burner is comprised of relatively inexpensive and simple In the use 1 disconnecting the leads and snapping the old switch from its supporting spring clip, inserting the new switch and connecting the leads.

The operation of my burner is fully automatic-to the extent of providing an automatic choke action for feeding a richer fuel mixture to the nozzle at the start of the combustion period, and to the extent of providing a blast of air at the end of each combustion period to dry the nozzle of excess fuel. Thus, my burner requires a minimum of attention from the householder or industrial user thereof for operation, cleaning or maintenance.

While I have described my invention as embodied in a specific form and operating in a specific manner for purposes of illustration, it should be understood that I do not limit my invention thereto, since various modifications will suggest themselves to those skilled in the art without departing from the spirit of my invention, the scope of which is set forth in the annexed claims.

I claim:

1. In a liquid fuel burner which includes a fuel supply system, an air supply system, and means for carburating fuel and air before ignition of a mixture thereof in a furnace; an electrothermal system for the automatic operation and safety control of said burner, comprising: an electrical power source; a main switch; a thermostatic switch; a safety switch; an electrical heating element connected in series with said main, thermostatic and safety switches across said source; a first thermostatic element disposed in association with and responsive to heat from said electrical heating element; a fourth switch made when said first thermostatic element is cold, and broken when said first thermostatic element is heated; fifth and sixth switches broken when said first thermostatic element is cold and made when said first thermostatic element is heated; a second electrical heating element for preheating said fuel connected in series with said fourth switch across said source; an electric motor for said fuel and air supply systems connected in series with said fifth switch-across said source; a transformer having the primary winding thereof and said sixth switch connected in series across said source; a fuel igniting spark gap connected in series with the secondary winding of said transformer; a solenoid connected in series with said main switch; said sixth switch, said safety switch and said thermostatic switch across said source, a fuel supply valve, said solenoid controlling the actuation of said fuel supply valve; a second thermostatic element responsive to the heat of combustion in said furnace; a seventh switch made when said second thermostatic element is cold, and broken when said second thermostatic element is heated; a thermostatic actuator including a resistance element in series with said seventh switch, both forming a shunt circuit about said solenoid; and means for breaking said safety switch by the energization of said resistance element thereby shutting off the fuel supply, the ignition spark, and said electric motor when combustion fails in said furnace.

2. An electrical system for the automatic and safety control of a liquid fuel burner comprising: an electrical power source; a main switch; a thermostatic switch; a safety switch; an electrical heating element connected in series with said main, thermostatic and safety switches across said source; fourth, fifth and sixth switchesmade and broken by thermostatic means responsive to heat from said electrical heating element, said fourth, fifth and sixth switches each being disposed as one element in each of three separate circuits across said power source, respectively, said fourth switch being in opposite phase from said fifth and sixth switches; a fuel preheating unit in series with said fourth switch; an electric motor for said burner in series with said fifth switch; a transformer having the primary winding thereof and said sixth switch connected in series across said source; a fuel igniting spark gap connected in series with the secondary winding of said transformer; a fuel supply valve; a solenoid controlling the actuation of said fuel supply valve connected in series with said sixth switch, said safety switch, said thermostatic switch, and said main switch; a seventh switch made and broken by thermostatic means responsive to the heat of fuel combustion; a thermostatic actuator including a resistance element connected in series with said seventh switch to form a shunt circuit about said solenoid; and means for breaking said safety switch activated by said resistance element adapted to shut off said burner when fuel combustion ceases.

3. A system for the automatic control of a liquid fuel burner comprising: an electrical power source; a thermostatic switch; an electrical heating element connected in series with said thermostatic switch in a circuit across said source; a heat activated control element adapted to be heated by said heating element, three switch members operatively connected to said control element, the first of said switch members being made when said control element is cold, and broken when said control element is heated, the second and third of said switch members being in opposite phase from said first switch; a second electrical heating element for preheating fuel I connected in series with said first switch in a second circuit across said source; an electric motor for said burner in series with said second switch in a third circuit across said source; a transformer having a primary and secondary winding; a fuel igniting spark gap formed by a pair of electrodes connected in serieswith the secondary winding of said transformer, said third switch and the primary winding of said transformer being connected in series in a fourth circuit across said source; a fuel supply valve; and a solenoid controlling the actuation of said fuel supply valve connected in series with said third switch and said thermostatic switch in a fifth circuit across said source.

JEFFERSON C. GIBSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,541,768 Diller et al June 9, 1925 1,594,020 Smith July 27, 1926 1,594,022 Smith July 27, 1926 1,608,271 Gibson Nov. 23, 1926 1,610,957 Lawrence Dec. 14, 1926 1,656,486 Huntington Jan. 17, 1928 1,679,331 Williams July 31, 1928 1,883,242 Bogle Oct. 18, 1932 2,028,807 Reiboldt Jan. 28, 1936 2,230,732 Tapp et al. Feb. 4, 1941 2,347,843 Hayfield May 2, 1944 2,369,530 Bulger Feb. 13, 1945 2,370,205 Tate Feb. 27, 1945 2,375,900 DeLancey -1 May 15, 1945 2,427,178 Aubert Sept. 9, 1947 

